1. Field of the Invention
The present invention relates to a microprinter and, more particularly, to a microprinter having a type belt for printing, for use in combination with an electronic calculator.
2. Description of the Prior Art
The microprinter having a type belt for printing has been applied to various equipment, particularly, small equipment, such as electronic calculators.
The conventional microprinter comprises a type belt, a driving belt pulley for driving the type belt, a motor for driving the driving belt pulley, a hammer supported for movement along a printing line to press a type on the type belt located at a printing position against a recording sheet, a ratchet wheel fixedly combined with the driving belt pulley for rotation together with the driving belt pulley, a main gear supported coaxially with the ratchet wheel for individual rotation to drive the hammer, a selector lever capable of selectively engaging the ratchet wheel or the main gear, and an electromagnetic clutch for controlling the motion of the selector lever.
The selector lever is engaged with the main gear to restrain the main gear, and then the motor is actuated to select a desired type by rotating the ratchet wheel and the driving belt pulley. Then, a current is supplied to the electromagnetic clutch to release the main gear from the selector lever and to engage the selector lever with the ratchet wheel to restrain the ratchet wheel. In this state, the motor drives the main gear to drive the hammer to press the selected type against the recording sheet for printing.
After the printing operation for one line has been completed, a current is supplied to the electromagnetic clutch and another electromagnetic clutch to transmit the rotative force of the motor to a sheet feed mechanism to feed the recording sheet by a distance corresponding to a line space.
Thus the conventional microprinter is provided with two electromagnetic clutches respectively for the printing mechanism and the sheet feed mechanism to drive the two mechanisms by a single motor.
However, since electromagnetic clutches require a comparative large space for installation, the provision of two electromagnetic clutches in a limited space is an impediment to forming the microprinter in a compact structure, which is essential to the microprinter, requires a comparatively large number of parts and increases the manufacturing cost of the microprinter.